Connect an ampere-meter between the pins of connector P22 as shown in
the figure below.

Figure 1. Current measurement with an ampere-meter

Note: An ampere-meter will measure the average current drawn by the nRF52840
SoC if:

The SoC is in a state where it draws a constant
current, or, the activity on the device changing load current, like BLE
connection events, is repeated continuously and has a short cycle time (less
than 100 ms) so that the ampere-meter will average whole load cycles and not
parts of the cycle.

The dynamic range of the ampere-meter is wide enough to give accurate
measurements from 1 µA to 15 mA.